Up until now it seems that it's intended purpose has been to facilitate and encourage rainfall where there has been a lack thereof.

Do you think it would be possible to use this technique as a weapon by, for example:

* infusing the clouds with something that could cause destructive percipitation (e.g. acid rain, radioactivity, poison, etc)? * starving a nation of it's rainfall and thereby causing drought and the consequences therof * on the flip side, creating so much rainfall that would cause mass flooding

Nah, don't think it works on a global basis. And if you want to kill people you always can use A bombs, mixing them with different rare earths, metals etc, to produce different effects. https://en.wikipedia.org/wiki/Dirty_bomb [Links inactive - To make links active and clickable, login or click here to register]

A neutron bomb is another variant, leaving infra structure standing, while killing of all biological. Pretty sick in my book.

Cloud seeding was used effectively at Chernobyl to fight the fire and precipitate radioactive dust to prevent it dispersing, but if you are going to drop nasties on your enemy it's better to do so directly.

It's interesting that you see it as a weapon against civilians. The nature of warfare has changed radically in the last 100 years! Whilst the possibility of widespread drought or flooding as a weapon of war is remote, it is certainly the case that armies find it a lot more difficult to move over wet ground, and are a lot more visible on snow. That said, modern warfare has become highly asymmetric and the open tank battles of WWII are unlikely to happen again. From Vietnam onwards, the mechanised side has always lost. Even in the Falklands, capital ships were destroyed or irrelevant and the decisive action was a series of small infantry skirmishes.